BRUSSELS – Passport-free travel and hassle-free business in Europe has never been in more danger.

With more than 1 million people streaming into the European Union hoping for sanctuary or jobs, nations have erected fences, deployed troops and tightened border controls.

“What we have worked for, for so many years, we are seeing it crumbling now in front of us,” Roberta Metsola, a leading EU lawmaker on migration, told The Associated Press on Tuesday.

As draconian as they might seem, most attempts to stem the migrant flow have been within the letter, if not the spirit, of the rules governing the European travel haven known as the Schengen area, a jewel in the EU’s integration crown

But as of mid-May, the EU is in uncharted waters. The legal options for countries like Germany, Austria and Sweden to impose ID checks on everyone who enters, including Europeans, begin to run out.

“Our citizens have a right to feel safe,” Metsola said. “If that means that we will need to keep stock of who is crossing our borders for a specific amount of time, then we will have to do it.”

The German government has signaled it’s unlikely to ease border controls on May 13, when its temporary border measures legally expire. If no other mechanism is in place by then, the Schengen rule book could effectively be suspended.

Most EU nations blame Greece for this. Some 850,000 people arrived there last year, many to the Greek islands after a short but often treacherous sea journey in smugglers’ boats from Turkey.

Aid groups estimate that Greece has shelter for barely 10,000 people; a little over 1 percent of those who need it. The Greek coast guard is totally overwhelmed.

Managing the country’s vast maritime border would challenge even an experienced government with a fully equipped public service. Greece, at the moment, is also consumed with a crippling economic crisis.

But, Metsola said, “there is a lack of knowledge as to who is coming in and who is going out, and that automatically increases fear and increases the security concerns.”

Most migrants don’t want to stay in Greece. Many hope to be find sanctuary in Germany or Sweden, and these countries and their neighbors say they will have to impose border controls if Greece can’t or won’t.

“It’s clear that if we can’t secure the European borders — that means the Greek-Turkish border — then the Schengen border will move to Central Europe,” Austrian Interior Minister Johanna Mikl-Leitner said Monday.

With Schengen under threat, few palatable options are available and time is running out.

The EU’s executive Commission is preparing a plan that could allow border checks in some countries to be extended for up to two years.

But the plan might take three months to introduce, which effectively means the Commission has about two weeks to get its work done, according to EU officials. EU leaders would debate the plan at a summit starting on Feb. 18.

The move involves establishing that there is “a serious and persistent deficiency” at one or more of Europe’s borders to the outside world. A status report on Greece is being drafted.

If a large majority of the EU’s 28 nations support it, border controls could be introduced for all people entering the rest of the Schengen zone from Greece, including Greek citizens.

The EU on Tuesday mulled allowing states in the Schengen zone to reintroduce border checks for up to two years to cope with the migration crisis, in what would be a blow to a cherished pillar of European unity.

At a meeting in Amsterdam on Monday EU interior ministers had asked the European Commission — the executive arm of the 28-nation European Union — about the possibility of extending the checks.

“We want to be prepared for all eventualities but we are not at the activation stage yet,” Natasha Bertaud, the Commission’s spokeswoman on migration, told reporters in Brussels.

“If the situation does not change and there could indeed be justifications under public order and security reasons to maintain internal controls at internal Schengen borders,” Bertaud added.

“We want to be prepared so we are pursuing the options that could be available to us under article 26 if and when we need to activate them.”

Article 26 of the Schengen code allows members of the 26-country zone, which includes most European Union countries, to reintroduce internal border controls for a maximum of up to two years under exceptional circumstances.

In the last few months, Austria, Germany, Denmark, Sweden, France and non-EU member Norway have all introduced temporary controls over the migrant crisis, but with a limit of six months.

The member states are required to inform the commission, which reviews whether they meet the criteria for reintroducing controls.

“We know the migratory flows are not going to be subsiding soon and as the weather changes are even likely to increase again,” Bertaud said.

The introduction of the temporary controls has raised fears that the Schengen zone could collapse.

The Czech Republic on Tuesday invited regional neighbors Hungary, Poland and Slovakia to a special summit on February to discuss the issue.

“We aren’t deciding merely about the future of the (passport-free) Schengen (area) … but also about the future of the entire European Union,” Czech Premier Bohuslav Sobotka said following talks in Slovakia with Slovak counterpart Robert Fico.

Fico, a left-winger known for his anti-immigrant rhetoric, meanwhile said the EU was committing “ritual suicide” with its migration policy.

The EU is already due to discuss the migration crisis at a summit of leaders in Brussels on Feb. 18-19, although the issue could be overshadowed by negotiations over Britain’s EU reform demands.

An extension of border controls has further sparked concerns that Greece — the landing point for around 80 percent of all migrants arriving in Europe — could be effectively frozen out of Schengen.

“If we do not manage to secure Europe’s external border, this is the Greek-Turkish border, the European external border will move towards Central Europe,” Austrian Interior Minister Johanna Mikl-Leitner said Monday.

Meanwhile, the Commission warned of possible steps against Pakistan if it fails to comply with a deal on deporting migrants of Pakistani origin.

The EU persuaded Pakistan in November to restore a suspended agreement to facilitate the return of Pakistani illegal immigrants without documentation.

Pakistan was one of the top five countries of origin among the 1 million migrants who arrived in Europe last year, although most are considered economic migrants rather than refugees from conflict.

“While discussions have been good and positive, we note that there are still difficulties with this readmission deal,” Bertaud said.

“The Commission is currently examining possible incentives — positive and negative — so that this accord is applied properly.”

In December, Pakistan sent back at least 30 undocumented migrants that Greece was trying to repatriate after saying Greece had failed to provide adequate proof that they were Pakistani, a claim later disputed by the EU.